Polyurethane elastomer not only has the high elasticity of rubber, but also the high hardness and high strength of plastic. It has excellent abrasion resistance, excellent oil resistance, chemical resistance, flex resistance, and low temperature resistance. Polyurethane elastomer is an ideal material for green tires and green tire manufacturing. Waste tires can be recycled and used as other polyurethane products without causing environmental pollution.
New trends in product development
Polyurethane thermoplastic elastomer, also known as thermoplastic polyurethane rubber, TPU for short, is a type of block linear polymer, A is a high molecular weight polyester or polyether, B is a glycol containing 2-12 linear carbon atoms , The chemical structure between AB segments is connected with diisocyanate, usually diphenylmethane diisocyanate. Thermoplastic polyurethane rubber is cross-linked by intermolecular hydrogen bonds or lightly cross-linked between macromolecular chains. As the temperature increases or decreases, these two cross-linked structures are reversible. In the molten state or solution state, the intermolecular force is weakened, and after cooling or solvent volatilization, they are connected by strong intermolecular force to restore the original solid properties. Polyurethane elastomer is a variety of polyurethane synthetic materials. Because its structure has two segments, soft and hard, it can be molecularly designed to give the material high strength, good toughness, wear resistance, oil resistance and other excellent properties. Because of its extremely excellent performance, it is widely used in many fields such as automobiles, construction, mining, aerospace, electronics, medical equipment, sports products, and has become a synthetic material product with great development prospects.
The global annual consumption of thermoplastic elastomers reaches 2.26 million tons. In order to better grasp this huge business opportunity and meet market demand, international rubber and plastic material manufacturers have been actively developing various new thermoplastic elastomer products. Thermoplastic elastomer products have a wide range of applications, and the demand for automotive and medical markets has increased the most.
Main performance characteristics
Polyurethane elastomer is a typical multi-block copolymer. The molecular chain is composed of flexible segments with a glass transition temperature lower than room temperature and rigid segments with a glass transition temperature higher than room temperature. Among them, oligomer polyols constitute flexible segments, and diisocyanates and small molecule chain extenders constitute rigid segments. The block structure of the flexible segment and the rigid segment determines the particularity of its performance:
Ordinary rubber hardness range is generally Sauer A20-A90, and the hardness range of plastic is about Sauer A95-Sauer D100;
High strength and elasticity, can still maintain high strength and elasticity in a wide range of hardness;
Excellent abrasion resistance, 2-10 times that of natural rubber;
Excellent resistance to water, grease and chemicals;
High impact resistance, fatigue resistance and vibration resistance, suitable for high frequency flexural applications;
good low temperature resistance, low temperature brittleness is about -30℃ or below -70℃;
has excellent thermal insulation performance, due to the low thermal conductivity, compared with rubber and plastic, the thermal insulation effect is better;
Good biocompatibility and anticoagulant performance;
Excellent electrical insulation, mildew resistance and UV stability.
Polyurethane elastomers can be molded by plasticizing, mixing, and vulcanizing processes like ordinary rubber, or they can be molded in the form of liquid rubber, poured centrifugal molding or sprayed, and can also be made into granular materials by injection, extrusion, and calendering. , Blow molding and other processes. In this way, not only the work efficiency is improved, but the dimensional accuracy and appearance of the product are greatly improved. The use of a pouring machine for pouring also avoids hidden defects that may be caused by manual pouring, and greatly improves the service life of the product.
Polyurethane elastomer is not perfect, its main disadvantages are:
The internal heat generation is large, and the high temperature resistance performance is average. The normal operating temperature range is -40-120℃. If it needs to work under high-frequency oscillation conditions or high temperature conditions for a long time, corresponding modification measures must be taken in the structural design or formula.
is not resistant to strong polar solvents and strong acid and alkali media. At a certain temperature, alcohol, acid, and ketone will swell and degrade the polyurethane elastomer. Solvents such as chloroform, dichloromethane, dimethylformamide, trichloroethylene will swell the polyurethane elastomer at room temperature.
Common functions and application areas
Because of the unique function of polyurethane elastomer, as a polyurethane elastomer polymer material with excellent performance, it has been widely used in people's daily life, industrial and agricultural production and many other fields.
Pouring polyurethane elastomer is a new type of material between rubber and plastic. In practical applications, it is mostly used as an updated product of rubber products. Due to its excellent wear resistance, high strength, high elongation, high elasticity, and a wide range of hardness; it also has excellent properties such as oil resistance, acid resistance, alkali resistance, and radiation resistance. It also has outstanding wear resistance, so it is There are many important applications for serious problems, especially in mining, oil, and natural gas industries. The applicable fields of castable polyurethane elastomer are: solid tires; printing and conveying rubber rollers; compression rubber rollers; oil seals, gasket ball joints, bushing bearings; ○-shaped rings; support cushions; soles, back roots, toecaps; linings; gears Wait. Different application fields have different hardness ranges for the selected elastomers. Applications in mining, metallurgy and other industries include sieve plates, shakers, etc.; applications in the machinery industry include rubber rollers, tapes, seals, etc.; applications in the automotive industry include tires, sealing rings, etc.; applications in light industry There are polyurethane sole materials, polyurethane synthetic leather, polyurethane fibers; applications in the construction industry include waterproof materials, paving materials, potting materials, etc.
Polyurethane foam material is currently the best thermal insulation product among all wall thermal insulation materials, and it is also the most forward-looking thermal insulation material in the world. It has light weight, thermal insulation, moisture resistance, sound insulation, heat resistance, shock resistance, corrosion resistance, It is easy to bond with other materials and does not produce droplets during combustion. It is widely used in building roofs, walls, ceilings, floors, doors and windows, etc., as thermal insulation materials. Rigid polyurethane foam is mainly used in heating, refrigeration, petroleum, chemical, automotive, transportation and other industries in my country, and its share of building wall insulation is less than 10%.
The polyurethane elastomer is firmly bonded to the metal frame, with large bearing capacity, abrasion resistance and oil resistance. It can be used to manufacture rubber wheels that are widely used in various transmission mechanisms, such as supporting wheels, guide wheels for production line conveyor belts, and pulleys for cable cars. In sports and entertainment, the wheels of high-end roller skates and scooters are made of polyurethane. Polyurethane rubber wheels also have the characteristics of oil resistance, good toughness, and strong adhesion. They are very effective when used on vehicles such as mining monorail cranes, rack cars and cleaning vehicles. Polyurethane is also used for small electronic and precision instrument transmission wheels, various universal wheels, etc. The use of PU elastomer inner lining molds can reduce production costs, and use in ceramic tile and ceramic production lines can improve production efficiency and yield. Using urethane molds can replicate various patterns and produce decorative blocks. In the metal mold stamping production, polyurethane elastomer rods, tubes and plate pads are used instead of metal springs as buffer members, which have high elasticity, flexibility, and high strength of original shrinkage without damaging the mold.
Coal mines, metal and non-metal mines are in great demand for non-metallic materials with high wear resistance, high strength and flexibility. Polyurethane elastomer products used in mines include sieve plates, elastomer linings, and conveyor belts. Others such as cyclones for solid separation, flame-retardant and anti-static wear-resistant conveyor belts, solid core wheels of mine monorail cranes, bonding plates for coal mine shotcreting machines, and oil seals on 10,000-ton electric wheel dump trucks Cold patching glue for ring, high-voltage cable sheath, etc.
Polyurethane thermoplastic elastomer
Thermoplastic elastomer is abbreviated as TPE/TPR. It uses SEBS and SBS as the base material. It is a kind of polymer alloy material with general plastic processing performance, and the product has similar cross-linked rubber performance. In multi-material molding, there are four basic types of thermoplastic elastomers, namely styrene block copolymers, thermoplastic vulcanizates, thermoplastic polyurethanes and copolyesters. Thermoplastic polyurethane elastomer, like cast polyurethane and mixed polyurethane, has high modulus, high strength, high elongation and high elasticity, as well as excellent wear resistance, oil resistance, low temperature resistance, and aging resistance.
TPU can be classified in different ways. According to the soft segment structure, it can be divided into polyester type TPU, polyether type TPU and polybutadiene type TPU, which respectively contain ester groups, ether groups or butene groups; according to the isocyanate structure used, it can be divided into yellowing type and non-yellowing type. The variants are divided into urethane type and urethane urea type according to the hard segment structure, which are obtained by diol chain extension or diamine chain extension respectively. According to the presence or absence of crosslinking, it can be divided into full thermoplastic and semi-thermoplastic. The former is a pure linear structure without cross-linking bonds; the latter contains a small amount of cross-linking bonds such as allophanate.
Polyurethane thermoplastic elastomers containing more urethane structural units in the main chain are generally called polyurethanes. Thermoplastic polyurethane elastomer is a type of polyurethane rubber. Its macromolecular chain structure is composed of polar polyurethane or polyurea segments and aliphatic polyester or polyether segments alternately. The intermolecular hydrogen bond cross-linking and the light cross-linking between macromolecular chains make this polymer material plastic. This cross-linked structure has plasticity with temperature changes. There are two types of thermoplastic polyurethane elastomers: polyester type and polyether type. High hardness, good abrasion resistance and good elasticity are the most prominent properties of this type of elastomer. In addition, the tensile strength, tear strength, chemical resistance and environmental resistance are also excellent, and the mechanical properties of some materials increase with the increase in hardness. The relative density of the thermoplastic polyurethane elastomer is generally 1.10-1.25, and the Shore hardness is 65A-80D. The low temperature resistance of polyether polyurethane is better than polyester polyurethane.
Thermoplastic polyurethane elastomer is the first elastomer that can be processed by thermoplastic technology. Polyurethane rubber has good wear resistance. Additives can improve its weather resistance, dimensional stability and heat resistance, reduce friction or increase flame retardancy. They have a wide range of applications in various hardness grades, involving automotive seals and Washers, stabilizer bar sets, medical catheters, pacemakers and artificial heart devices, mobile phone antenna gears, pulleys, sprockets, chute linings, textile machinery parts, casters, washers, diaphragms, couplings and vibration damping components.
Polyurethane elastomer before application and development trend
The global consumption of polyurethane rubber elastomers is rising rapidly year by year. Foreign authoritative organizations predict that the world will maintain a growth rate of 7%-8% in the next few years. Among them, the automobile industry and the shoe industry are the main consumer markets for polyurethane elastomers, and the consumption growth is the fastest. Two major areas. The main international manufacturers of polyurethane elastomers are: Goodrich Company, Mobay Company, Dow Chemical Company, Huntsman Company, Bayer Company of Germany, Asahi Glass Company of Japan, Kyowa Fermentation, NOK Company, etc. Among them, Bayer and Huntsman mainly focus on shoe materials, while Dow Chemical, Asahi Glass, NOK and Concord Fermentation focus on automotive mechanical parts. At present, these major production companies continue to introduce new varieties to expand to surrounding areas.
The domestic market’s demand for polyurethane is increasing year by year, but some key raw materials are still mainly imported, which restricts the development of the polyurethane industry. my country should accelerate the localization of the production of key raw materials and produce raw materials with excellent performance and low prices. The alloying research of polyurethane elastomer materials has also become a hot topic in the research of polymer materials in recent years. Polyurethane elastomer can be compounded with various synthetic resins such as PVC, PE, ABS, etc. to reduce costs and improve performance. Polyurethane elastomers can also be modified by adding some organic fillers to highlight or strengthen certain aspects of performance, or to overcome some of the shortcomings of polyurethane elastomers to meet special needs. With the increasing requirements for polyurethane elastomer products and the strengthening of people's environmental awareness, the development of new aliphatic polyisocyanates has also become an urgent research topic. Technicians use the natural structure and characteristics of biological resources to produce polyurethane elastomer products that can be decomposed by microorganisms like wood. At present, some Japanese companies mix natural raw materials such as wood powder, sucrose and waste coffee into polymer polyols to prepare polyurethane elastomers, which can reduce the amount of polyols, reduce production costs, and give products biodegradability. A certain number of commodities have already come out.
In recent years, the research on liquid crystal polyurethane elastomers has been relatively active, mainly focusing on the selection of raw materials, the optimization of process routes and the improvement of physical properties. Liquid crystal polyurethane is formed by connecting rigid mediators and flexible spacer groups. It is a polyurethane elastomer with liquid crystal properties in the melt state. The material has good mechanical, thermal stability, high elasticity, high elongation and processing properties. The synthesis of liquid crystal polyurethane elastomer can adopt a one-step or two-step polymerization method, and the processing and molding processes are diverse, including extrusion, injection, molding and coating. The blending modification of synthetic materials has become one of the current research and development focus of polymer compounds. Polyurethane elastomers can be blended and modified with PVC, PV, PE, ABS and other synthetic resins to reduce production costs and improve physical and processing performance.
Environmental protection is another major issue facing the rising polyurethane industry. As polyurethane materials are used more and more widely in the national economy, and the amount used is increasing, the recycling and reuse of its waste has also received increasing attention. Waste polyurethane mainly includes scrap from the corners of the production plant, mold spills, scrapped cars, polyurethane foam and elastomer waste shoe soles in refrigerators, waste PU leather, and spandex old clothes. Currently, there are three main methods for recycling polyurethane: physical method, chemical method, and energy method. Regarding the recycling of waste polyurethane products, the European Union has taken the lead in promulgating the laws and regulations on the recycling of waste plastics from electrical products: who produces it and who recycles it. my country should also speed up the recycling of polyurethane products, especially foam products.
Polyurethane elastomer as a new type of material has been gradually applied to all walks of life, and its role is becoming greater and greater. With the development of the construction industry, people’s awareness of environmental protection is gradually increasing, and new technologies for polyurethane elastomers continue Appear, polyurethane elastomer will be more and more widely used in the construction industry.